- Have discontinued previous treatments for cancer and recovered from the acute effects of therapy (for example, at least 42 days for mitomycin-C or nitrosoureas, 28 days for other chemotherapy and biologics. At the discretion of the investigator, hormone refractory prostate cancer patients who are stable on gonadotropin-releasing hormone (GnRH) agonist therapy and breast cancer patients who are stable on antiestrogen therapy (for example, an aromatase inhibitor) may continue treatment